Summary and Analysis

Animal Behavior: Learning

Terms

Problems

Non-associative Learning

Most animals show some degree of non-associative learning. This means they
change their response to a stimuli without association with a positive or
negative reinforcement. Animals frequently subjected to a stimulus will often
become habituated to that stimulus--they will show a reduction or total
elimination of response to a stimulus without positive or negative
reinforcement. If you poke them, sea slugs (Aplysia) will curl inwards.
However, if you poke them repeatedly, the response will become less and less
extreme until they do not withdraw at all. When presented with a novel
stimulus, such as an electric shock, the sea slugs will recover their withdrawal
response to poking. This phenomenon in which the habituation disappears is,
conveniently, known as dishabituation. Furthermore, the sea slugs can be
sensitized, whereby they will show an increased response to poking after
first being presented with a strong or novel stimulus. The difference between
dishabituation and sensitization is that dishabituation involves the recovery of
the original response while sensitization produces a response stronger than the
original one.

Associative Learning

Classical Conditioning

In 1902, the Russian physiologist, Ivan Pavlov, began his famous experiments on
conditioning. Pavlov repeatedly presented a dog with food following the ringing
of a bell. When the bell sounded without the presentation of food, the dog
would still respond to the bell as if it were food. Pavlov collected the dogs'
saliva and found that the amount of saliva produced by bell ringing increased as
the dogs were more frequently exposed to the coupling of food presentation and
bell ringing. The dog had learned to associate the sound of the bell with food.
Pavlov called the food an unconditional stimulus, or UCS, because the dog's
normal reaction would be to salivate at the presentation of food. The bell he
termed the conditional stimulus, or CS, because response to the bell was
conditional upon the association between the bell and food. For the same
reasons, salivation in response to food was labeled the unconditional
response, or UCR, while salivation in response to the bell was called the
conditional response, or CR. Conditioning the dog to salivate at the sound
of the bell occurred as a result of a contingency between the UCS and the CS.
Pavlov's experiment was an example of positive conditioning. It is also possible
to negatively condition an animal by using an unpleasant UCS.

Operant Conditioning

In classical conditioning, the animal receives no benefit from associating
the CS with the UCS. However, in operant conditioning, an unassociated
behavior becomes associated with a reward. B.F. Skinner designed an apparatus
called a "Skinner box" to test the interaction between UCS and CS. A rat was
placed inside the Skinner box; if the rat pressed down a lever inside the box
then the box would release a food pellet. Soon, the rat pressed the lever far
more often than he would just by chance. Most likely, the first time the rat
pressed the lever it was by chance. But with each instance of lever pressing,
the operant is reinforced by reward with food. The rat learns that pressing the
lever is associated with food, and so he will increasingly press it. Almost any
operant and reward system can be used effectively.